The present disclosure relates to an optical scanning device and an image forming apparatus, and in particular relates to technology of adjusting the light quantity of a laser beam that is used for scanning a photoreceptor.
Conventionally, known is technology of forming a latent image on a peripheral face of a photoreceptor in an optical scanning device provided in an image forming apparatus by reflecting (deflecting) a laser beam emitted from a light source toward the photoreceptor with a rotating polygon mirror or the like, and causing the laser beam to scan the peripheral face of the photoreceptor. Upon writing the latent image with the laser beam, the laser beam passes through a condenser lens before reaching the peripheral face of the photoreceptor. It is known that the exposure value of the laser beam will differ depending on the scanning position on the peripheral face of the photoreceptor due to characteristics of the optical element such as the difference in transmittance between the end part and the center part of the condenser lens.
There is conventional technology which uniformly corrects the exposure value of the laser beam based on the scanning position, as described above. A beam scanning-type image forming apparatus based on this conventional technology includes light source means which generates a laser beam, deflection means which deflects the laser beam generated by the light source means, and scanning/imaging optical means which condenses the laser beam deflected by the deflection means as a light spot on a surface to be scanned, for scanning of the surface to be scanned. With this beam scanning-type image forming apparatus, the scanning position of the light spot is detected, and the light quantity of the light source is controlled in association with the scanning position of the light spot based on the light quantity correction data that has been predetermined corresponding to the detected scanning position.
The foregoing light quantity correction data is stored in the storage means for each of the sections, which are obtained by equally dividing the entire scanning position of the light spot into a predetermined number of sections. In addition, when the light spot is to scan such equally divided sections, the light quantity is corrected by using the light quantity correction data corresponding to the sections, which is stored in the storage means. The value of the light quantity correction data (light quantity correction value) is, for example, set to be great at the both ends of the scanning area and set to be small near the center of the scanning area, mainly in order to avoid the deterioration in the light quantity when the light beam passes through the end part of the lens.
Nevertheless, since the change in the exposure value is great at the both ends of the scanning area of the photoreceptor, it is necessary to divide the area more finely in order to ensure the correction accuracy near the both ends of the scanning area of the photoreceptor. Consequently, there was a drawback in that the number of storage units, such as registers, for storing the light quantity correction value corresponding to the finely divided areas increases.